Over the years, several different devices have been developed to temporarily occlude blood vessels during surgery. These devices are widely varied and include many different configurations. Clamps have become an increasingly popular device of choice and a wide variety of clamp types have been developed for use in vascular surgery.
Clamps are available in both large and small sizes. Larger clamps typically have large shafts or handles and are most suitable for occluding larger blood vessels in surgery procedures where sufficient space is available at the surgical site. Small surgical clamps are ideal for use with smaller vessels in microvascular surgery where little space is provided.
Popular small clamps include “bulldog” clamps. “Bulldog” clamps are small clamps that are applied to a blood vessel with the thumb and forefinger or with another surgical instrument such as forceps or an applier. The clamps are then left on the blood vessel until they need to be removed. Two known reusable “bulldog” clamps include the Acland clamp (distributed by S&T located in Switzerland) and the VAS clamp (distributed by Microsurgery Instruments, Inc. from Bellaire, Tex.). Other known disposable bulldog clamps include the BEAR™ vessel clamp (Arosurgical Instruments Corporation of Newport Beach, Calif.), the Biover microvascular clamp (distributed by Biover AG of Switzerland), and the Vascu-Statt® clamp (distributed by Scanlan International, Inc. located in St. Paul, Minn.).
Bulldog clamps typically include two jaws each having handles and connected together at a pivot point. Some clamps also include a means, such as a spring, for biasing the handles against each other and thereby imparting a closing force between the jaws (hereinafter, “biased clamps”). Typically, a spring is positioned between the handles to bias the handles away from each other and to impart a closing force between the jaws. When a surgeon desires to open the jaws, the handles can be pushed together against the biasing of the spring to cause the jaws to open. Known clamps that include a spring are the STEALTH™ surgical clip (distributed by Applied Medical Resources, Inc. located in Rancho Santa Margarita, Calif.) and the Novaclip™ (distributed by Novare Surgical Systems, Inc. located in Cupertino, Calif.). Other exemplary spring clamps are described in U.S. Pat. No. 3,805,792 to Cogley, U.S. Pat. No. 4,165,747 to Bermant, U.S. Pat. No. 4,931,058 to Cooper, and U.S. Pat. No. 5,683,405 to Yacoubian et al., the entire teachings each of which are herein incorporated by reference. While all of these are varied in their designs and configurations, all employ a spring to aid in creating a closing force of the jaws about a vessel. Spring clamps are especially advantageous in that they are easy to use during surgery.
One problem associated with biased clamps is that the closing force exhibited by the jaws may cause damage to the vessel. For example, the closing force may be too strong for the particular vessel used, so that the jaws exhibit a pinching and crushing effect on the vessel. Also, when the jaws of most clamps are in a closed position about a blood vessel, the contact surfaces of the jaws are not maintained in a parallel relationship along the length of the jaws. Rather, the contact surfaces of each jaw become more and more spaced apart along the length of the jaws and over the diameter of the blood vessel. As a result, the closing force tends to vary along the length of the jaws, with the closing force being the strongest at the position closest to the jaw handles and being the weakest at the position farthest from the jaw handles. When used on a blood vessel, the section of the vessel held by the area of the jaw having the strongest closing force will be pinched more than the vessel section held by the area of the jaw having the weakest closing force. In either case, these overly strong or uneven closing forces may result in permanent occlusion of, or traumatic damage to, the vessel.
Others have tried to minimize the potential for vessel damage by modifying the closing force of the clamps on the vessels. For example, some have developed clamps that include mechanisms for adjusting the closing force during surgical use (hereinafter “adjustable clamps”). These adjusting mechanisms allow a surgeon to change the closing force to conform to the particular type and size of the vessel being occluded. Known adjustable clamps are described in U.S. Pat. No. 5,011,487 to Schichman, U.S. Pat. No. 5,103,839 to Schichman, and U.S. Pat. No. 5,733,295 to Back et al. the entire teachings of each of which are herein incorporated by reference. Also, some adjustable clamps have employed jaws with contact surfaces having a substantially parallel relationship to one another, so that when adjusted, the clamps have a uniform closing force along the length of the jaws. An example of such an adjustable clamp is the Greyhound™ adjustable spring clip (distributed by Novare Surgical Systems, Inc.). While these adjustable clamps provide certain advantages, they are often more difficult to use during surgery than the biased clamps. It is time consuming and cumbersome for a surgeon to have to adjust the closing force, particularly during the wet and slippery conditions of surgery. Adjustable clamps also tend to be more susceptible to operator error than the biased clamps which have a preset closing force.
Therefore, it would be desirable to provide a clamp incorporating the ease of use associated with the non-adjustable, biased clamps as well as the ability to ensure that the closing forces are uniform along the length of the jaws associated with the adjustable clamps. It would be particularly desirable to provide a biased clamp having contact surfaces that are maintained in a substantially parallel relationship when positioned about a blood vessel, so that uniform closing forces will be imparted along the length of the jaws and over the diameter of the vessel.